The present invention relates to an apparatus, for a motor vehicle having a liquid-cooled engine, for heating windshield washer liquid or the like. The apparatus includes a cylindrical heat-exchanger housing that, via hose connectors that are disposed at both ends of the housing, can be disposed directly in the coolant line between the engine and a radiator, with the interior of the housing, through which the coolant flows, containing a tube coil that is helically wound in the longitudinal direction of the housing. The liquid that is to be heated flows through the tube coil, and the ends of the latter are conveyed out of the housing in a radial direction.
Various apparatus are known for motor vehicles in order to be able to utilize the heat that is released by the engine and is to be withdrawn by the cooling water of the radiator in a heat exchanger for generating warm windshield washer liquid. German Pat. No. 32 32 371, Gercken dated May 21, 1987, discloses a heatable windshield washer apparatus, the heat exchanger of which is disposed in the cooling water hose circuit and comprises a tubular housing through which the cooling water flows. Disposed coaxially in this housing is a double-walled tube, the hollow space of which forms the heat-exchanger channel for the wash liquid. The two connector fittings that are connected to the wash-liquid line and that lead to the hollow space of the double-walled tube project radially from this tube and extend through the wall of the housing. With such a heat-exchanger configuration, the double-walled tube can be placed axially in the tubular housing only without the connector fittings, and the latter can be inserted through the wall of the housing only after the double-walled tube is placed in the housing, whereupon the connector fittings must be connected to the double-walled tube in the housing. This requires a complicated and expensive manufacturing procedure. German Offenlegungsschrift 21 12 473, Nitterl et al dated Oct. 5, 1972, corresponding to U.S. Pat. No. 3,756,510, Nitterl et al, dated Sept. 4, 1973, discloses a heat exchanger for a heatable windshield washer apparatus, the tubular housing of which, through which cooling water flows, being closed off at the ends by end caps that are placed thereon and that contain hose connectors. A tube coil that is helically wound in the longitudinal direction of the housing is disposed in the latter as a heat-exchanger channel for the wash liquid. The connection ends of the tube coil for the wash liquid line project out through openings of the tubular housing or of the end caps; in particular, at one heat-exchanger end, a connection end projects out radially, and at the other heat-exchanger end, a connection end projects out at an inclined angle to the longitudinal axis of the housing. The tube coil can be installed in the housing only if the connection end that is inclined at an angle is first directed axially, so that when the tube coil is introduced into the tubular housing with this connection end in front, it can pass through the tubular housing. After the tube coil has been placed in the tubular housing, this connection end is then bent into the desired or required inclined position. Such a procedure can, of course, lead to damage of the material of the tube coil. This heretofore known heat-exchanger configuration additionally requires significant manufacturing effort in order to sealingly and securely connect the end caps to the tubular housing, for example by sealingly welding the abutting or overlapping edges of the sheet-metal housing and the cap all the way around. Significant manufacturing effort is also required in order to reliably seal the connection ends of the tube coil in the pass-through openings of the tubular housing or of the end caps to prevent cooling water from escaping from the heat exchanger; this can be accomplished, for example, by soldering a copper tube coil into the passthrough openings of the tubular sheet-metal housing and the caps.
It is an object of the present invention to provide an apparatus of the aforementioned general type that can be assembled in an easier, quicker, and more economical manner, of prefabricated individual components, than was possible with the aforementioned known types of heat exchangers, and that, especially at those locations where the connection ends of the tube coil are conveyed out of the heat-exchanger housing, and even at possible increased pressures in the cooling liquid circuit, assures a seal that reliably precludes loss of cooling water, which would, of course, be dangerous for the engine.